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I have a P4 2.6c with hyperthreading. I can't use a kernel without multi-cpu support activated (the kernel boot sequence stops). Have you heard about problem with hyperthreading? In fact I tried to compile my kernel without multi-cpu support because linux was very slow...
Distribution: RH 6.2, Gen2, Knoppix,arch, bodhi, studio, suse, mint
Posts: 3,304
Rep:
turn off hyperthreading in the bios, if you wish.
i asked a friend of mine who was working on it at the
time for intel, if it would be possible to turn it on and
off on the fly, with a utility. he said that idea had popped
up in meetings, but the way hyperthreading was
implemented, that wouldn't be possible without a chip
redesign.
i was trying to get him to bitch the guys into making
hyperthreading where you could turn it on or off on
the fly for testing software with it.
Thanks for your answers... I have a gentoo distribution and the kernel must be a 2.4.30 or something like that (I am not on my computer right now and I can't check that more precisely). As whansard told me, I will turn off hyperthreading for the moment and wait for kernel's updates. Do you know how I could measure global performances of my computer under linux? (a benchmark or something like that)
I just downloaded kernel-2.4.21 from kernel.org, compiled it, and the hyperthreading works just fine on my system. I have RedHat, and I downloaded the smp kernel from their rpm database, installed it, and tried to reboot - it was a no go. Not sure, but the hyperthreading seems a little unforgiving when it comes to hardware setup.
>gain on applications that scale well with multiple processors. That
>means single threaded applications (word, games, _most_ consumer apps)
>will get little if any gain and might even degrade a percent or so.
>Applications that we've seen perform the best with HT have been DCC
>(digital content creation) applications like 3ds max, Maya, and
>Photoshop where gains have been up to 70% with some workloads. Gains
>seen are VERY workload dependent. You really can't say that with HT,
>Maya gains 40% because there are some workloads that have no gain and
>some that even degrade. My job have been trying to mitigate those
>losses and help others do the same so that no application slows down
>with HT. One of the big issues that will come up is that some consumer
>applications fail with multiple processors because they were never
>tested for thread safety. When they crash, we hope it's not seen as an
>HT problem...
>
>Unreal ~3%, Quake ~2% gain. Internally, we've had a team that has
>threaded the LAME encoder and we see around a 50% increase.
Many thanks to all of you for your help. Whansard, thanks for your useful links about hyperthreading : it was really interesting.
Cropcircle, I will try your benchmarks later : I have to compare my old athlon with a p4...
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